1. Field of the Invention
The present invention relates to a method to characterize and compensate transceiver non-idealities. The non-idealities may be transmitter and receiver quadrature imbalance, carrier feedthrough and dc-offset.
2. Description of the Related Technology
As transceiver design, especially multi-mode transceiver design, hardly meets required radio performances, numerous calibration methods have been proposed. Focusing on the digital calibration methods, they are all facing the same problem: how to generate and capture the RF signal efficiently. Most prior art methods solve this problem by increasing the circuit cost and complexity.
A method requiring a limited amount of additional circuitry is presented in US2006/0034356. A transmission/reception arrangement and a method are provided to reduce non-linearities in the output signal from a transmission/reception arrangement. When calibration is required, the transmission/reception arrangement disables normal operation and turns to calibration mode. This involves not only deactivation of the normal baseband signal processing but also connection between the transmission and reception paths. A test signal is produced and supplied to the arrangement. Optimization of the arrangement's characteristics is based on an approach which iteratively searches a minimum of the error signal power, e.g. LMS algorithm. A measuring apparatus evaluates the test signal and assesses the power of this error signal. If the power is below a certain threshold, the optimization is halted. Then, calibration is terminated and the normal operating mode is restored.